The present invention relates generally to a new engine for use in, for example, personal watercraft. In particular, the present invention relates to a new four-stroke in-line engine that was developed with a view to the future stricter environmental and emission regulations. The engine has a power take off assembly located on one end for housing a plurality of engine components. This arrangement locates most of the engine component connections within a single housing. Furthermore, the connection assembly within the power take off housing permits the operation of multiple engine components with a single connection to the engine crankshaft.
There is a very popular type of watercraft known as a xe2x80x9cpersonal watercraftxe2x80x9d which is designed to be operated primarily by a single rider. Although this type of watercraft is commonly employed for single riders, frequently provisions are made for accommodating additional passengers although the maximum number of passengers is more limited than conventional types of watercraft.
This type of watercraft is also generally quite sporting in nature and normally accommodates at least the rider on a type of seat in which the rider sits in a straddle fashion. The passenger""s area is frequently open through the rear of the watercraft so as to facilitate entry and exit of the rider and passengers to the body of water in which the watercraft is operating, as this type of watercraft is normally ridden with passengers that are wearing swimming suits.
These personal watercraft are generally quite small so that they can be conveniently transported from the owner""s home to a body of water for its use. Because of the small size, the layout of the components is extremely critical, and this gives rise to several design considerations that are peculiar to this type of watercraft. However, due to its sporting nature, it is also desirable that the watercraft be powered by an engine and propulsion device that is not only efficient but also generates sufficient power.
Traditionally, two-cycle engines have been used to power watercraft, including personal watercraft. These engines have the advantage that they are fairly powerful, relatively lightweight, and compact.
One particular disadvantage to the two-cycle engine is its emission content. Two-cycle engines generally exhaust larger quantities of hydrocarbons and other pollutants than four-cycle engines due to cylinder charging inefficiencies and the combustion of lubricating oil among other things. When measures are taken to reduce emissions of the two-cycle engine, other generally undesirable consequences can result, such as an increase in the weight of the engine, a reduction of its power output or the like. With concern for the environment and increasingly strict emissions requirements being instituted by various governing bodies. There is motivation to provide a power plant that reduces exhaust emissions while retaining other advantageous characteristics such as compactness, low weight and high power output.
Four-cycle engines are commonly used as power plants in other applications, such as automobiles. These engines have the advantage that their emissions output are generally desirably lower as compared to a two-cycle engine for a given power output.
Four-cycle engines are generally larger than two-cycle engines and present numerous design problems when locating the engine in a relatively small personal watercraft. These engines typically include starter assemblies, generators, cam shafts, etc. There, however, is no centralized location for interconnecting these elements, which leads to larger engine sizes and a greater potential for water penetration in water environments
It is an object of the present invention to provide a four stroke, in-line engine having a compact construction.
It is another object of the present invention to provide a four stroke, in-line engine having a modular construction to permit the interchange of parts between various engine models.
It is another object of the present invention to provide a four stroke, in-line engine having improved exhaust emission characteristics.
It is another object of the present invention to provide a four stroke engine having a narrow and low profile.
It is another object of the present invention to provide a four stroke engine having a low profile valve actuation assembly for controlling the operation of the intake and exhaust valves.
It is another object of the present invention to provide a cylinder head having a low profile to reduce engine height.
It is another object of the present invention to offset the placement of the intake valves and exhaust valves with respect to a vertical axis within the cylinder head to reduce engine height.
It is another object of the present invention to provide an improved spark plug mounting assembly for easy access within the cylinder head.
It is another object of the present invention to provide a Y-shaped intake rocker arm assembly providing a compact construction.
It is yet another object of the present invention to provide a four stroke engine having an improved oil collection system and oil holding tank.
It is another object to provide a four stroke engine which combines a closed loop cooling system and an open loop cooling system for enhanced cooling of the engine in accordance with the present invention.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open loop cooling system enhances cooling of the crankcase and cylinder head.
It is another object to provide an open loop cooling system for cooling an exhaust manifold in accordance with the present invention, wherein the open cooling system lowers the temperature of the exhaust manifold such that the exhaust manifold functions as a heat sink for the crankcase and cylinder head.
It is another object of the present invention to provide a closed loop cooling system for selectively cooling the crankcase and cylinder head of the four stroke engine.
It is another object of the present invention to provide a closed loop cooling system having a selectively operable heat exchanger.
It is another object of the present invention to provide a supercharger for enhanced engine performance.
In accordance with the present invention, a four stroke internal combustion engine is disclosed having a power take off housing located at one end of the engine. The engine includes a crankcase having a crankshaft that is rotatably mounted therein. The crankshaft extends from one end of the crankcase. A cylinder head is connected to the crankcase. The crankcase and the cylinder head form at least one cylinder. Each cylinder includes at least one intake valve and at least one exhaust valve. A valve actuation assembly is located in the cylinder head and operates the intake and exhaust valves. A cam shaft is located in the cylinder head and operatively connected to the valve actuation assembly. In accordance with the present invention, the crankshaft is operatively connected to a drive shaft and the cam shaft. Furthermore, the crankshaft is operatively coupled within the power take off housing to at least one of a generator, an engine starting mechanism, a balance shaft, and a supercharger.
In accordance with the present invention, the connecting assembly connects the crankshaft to the drive shaft. The connecting assembly includes a connecting sleeve connected between an end of the crankshaft and an end of the drive shaft. The one end of the connecting sleeve is threadably connected to one of the crankshaft and the drive shaft. Another end of the connecting sleeve includes a plurality of teeth for engaging the other of the crankshaft and the drive shaft. The plurality of teeth engage at least one arcuate tooth on one of the crankshaft and the drive shaft. The teeth are lubricated by the engine lubrication system. The lubricant may be fed through a passageway in the crankshaft.
The crankshaft has a rotating member secured to thereto within the power take off housing. The rotating member is operatively coupled to at least one of the generator, the engine starting mechanism, the balance shaft and the supercharger. It is preferable that the rotating member includes a plurality of rotating gears.
The engine in accordance with the present invention may include a supercharger having a mounting portion that is positioned within a mounting opening in the power take off housing. The supercharger has an inlet portion having an inlet opening for drawing a stream of air, a blower located within the air inlet portion and a blower drive shaft connected to the blower. The blower drive shaft is rotatably mounted within the mounting portion. The blower drive shaft is operatively connected to one of the rotating gears through a connection assembly.
The connection assembly dampens the transmission of vibrations from the crankshaft to the blower drive shaft. The connection assembly includes a blower drive pinion located on one end of the blower drive shaft and a biased intermediate member located on the one end of the blower drive shaft. The biased intermediate member applies a force on the blower drive pinion such that the blower drive pinion is engaged with one of the rotating gears.
In accordance with the present invention, one of the rotating gears may engage the engine starting mechanism. The engine starting mechanism includes an engine starter, a drive pinion located within the power take off housing, and a linking mechanism located within the power take off housing. The drive pinion is adapted to engage the rotating gear during an engine startup operation. The linking mechanism provides a force on the drive pinion during the engine startup operation such that the drive pinion engages one of the rotating gears.
In accordance with the present invention, one of the rotating gears may be operatively connected to the balance shaft within the power take off housing. The balance shaft is parallel to and spaced from the crankshaft within the crankcase.
The valve actuation assembly includes a cam shaft that is rotatably mounted within the cylinder head. One end of the cam shaft extends from the cylinder head into the power take off housing. One of the rotating gears is operatively coupled to the one end of the cam shaft. A linkage connects the cam shaft to the gear.
In accordance with the present invention, a tensioner may be provided for adjusting tension in the linkage. The tensioner includes a spring biased tension adjustment element and a tensioning rail in contact with the linkage. The spring biased tension adjustment element applies pressure on the tensioning rail such that the tensioning rail maintains a predetermined tension in the linkage. It is also contemplated that the tensioner may be hydraulically biased.
The generator is operatively coupled the rotating member. The generator includes a stator secured to the power take off housing and at least one magnet. The magnets rotate around the stator on a rotatable magnet wheel that is secured to the rotatable member.
In accordance with the present invention, the four stroke internal combustion engine further includes a cooling system for cooling at least one of the crankcase and the cylinder head. The cooling system cools the at least one cylinder and includes a coolant flowing through at least one passageway in the crankcase and the cylinder head. The cooling system includes a cooling pump secured to the power take off housing for pumping the coolant through the at least one passageway and a heat exchanger for selectively removing heat from the coolant fluid at predetermined engine operating conditions.
The cooling pump includes a pump lid secured to the power take off housing. The pump lid and the power take off housing form a pump casing. The cooling pump includes a pumping drive shaft. The pumping drive shaft extends into the power take off housing.
The four stroke internal combustion engine also includes a lubrication system for providing lubricating fluid to the engine. The lubrication system includes a lubricant pump for pumping lubricant. The lubricant pump is located within the power take off housing. The lubricant pump is operatively connected to the cooling pump. The cooling pump and the lubricant pump are both driven by the pumping drive shaft.